1. Field of Invention
The present invention relates to flexible lustered products used, for example, as automobile radiator grilles. More particularly, the present invention relates to flexible lustered products having a base material formed from flexible resin and a surface with metallic luster.
2. Brief Description of Related Art
As shown in FIG. 8, a typical flexible lustered product 51 includes a base material 52, which is formed from a material such as polyurethane, a base coat layer 53, which is a coating applied to the base material 52, a metal film layer 54, which is applied to the base coat layer 53, and a top coat layer 55, which is applied to the metal film layer 54. The base coat layer 53 has a mirror smooth surface to enable satisfactory application of the film layer 54. The top coat layer 55 protects the film layer 54.
The metal film layer 54 is formed from a continuous film that results in several problems. For example, the application of an external force to the lustered product 51 may result in distortion or deformation of the product 51. Among the elements constituting the lustered product 51, the base material 52, the base coat layer 53, and the top coat layer 55 restore their original form regardless of the application of the external force. However, since the film layer 54 is made of a single sheet of metal film, there is a limit to the deformation amount which the film layer 54 can tolerate. As shown in FIG. 9, when the lustered product 51 is bent by a large external force, the film layer 54 cannot follow the deformation of the base material 52 and the layers 53 and 55. Thus, a relatively large stress acts on the film layer 54. This may form cracks 56 in the film layer 54. The cracks 56 appear as white streaks and thus deteriorate the outer appearance quality of the lustered product 51.
Japanese Unexamined Patent Publication No. 9-70920 describes a metal film layer that solves the above problems. The metal film layer is made of an anticorrosive metal and has a thickness of at least 150 .ANG. and at most 180 .ANG.. The metal film layer also has grain boundaries.
When an external force acts on the flexible lustered product of Publication No. 9-70920, the base material, which is made of a flexible resin material, the base coat layer, and the top coat layer deform in accordance with the external force. The fine metal particles constructing the metal film layer are visually perceived as a flat metal film. However, due to the grain boundaries of the metal film layer, the application of an external force just moves adjacent crystal grains (metal grains) apart from each other and widens the distance between the crystal grains. This suppresses the formation of cracks and prevents deterioration in the quality of the outer appearance of the product. In addition, the anticorrosive property of the film layer prevents corrosion.
However, the metal film layer of the above publication is still problematic in that the adhesion of the metal film layer to the base coat layer and the top coat layer is insufficient. This is because the base coat layer and the top coat layer are made of a resin material. Therefore, when the lustered product is used under harsh conditions or over a long period of time, the base coat layer and the top coat layer may peel off the metal film layer.